ADSORPTION ISOTHERM, KINETIC AND THERMODYNAMIC STUDIES FOR REMOVAL OF TOTAL DISSOLVED SOLID FROM PAINT WASTEWATER USING ACID MODIFIED MUCUNA SHELL
Present study was conducted to investigate the removal of total dissolved solid (TDS) from paint wastewater (PW) by using eco-friendly biomass of phosphoric acid modified mucuna shell (MSA). Characterization of MSA is done by (i) proximate analysis (ii) surface chemistry by FTIR (iii) surface physical morphology by SEM technique (iv) structural analysis using X-ray diffractometer. Batch experiment was carried out to determine effect of parameters such as pH, biosorbent dose, contact time and temperature. Adsorption capacity of the experimental results was fitted into four isotherm model; Langmuir, Freundlich, Temkin and Dubinin-Radushkevich, but the Freundlich isotherm model was found to have higher correlation coefficient, implying MSA had heterogeneous surface. The adsorption kinetic has been described by pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion model. It was observed that the rate of TDS adsorption follow pseudo-second-order model. Free energy of adsorption (∆G^o), enthalpy (∆H^o) and entropy (∆S^o) changes are calculated to know the nature of adsorption. The calculated value of ∆G^o at 303K-323K indicates that the adsorption process is spontaneous. From the calculation, values of ∆H^o and ∆S^oshows positive sign, which indicates that the adsorption process is endothermic in nature and the positive,∆S^osuggested increased randomness at the solid/interface.